a) Field of the Invention
The invention is directed to a vacuum valve comprising a valve body with a valve opening, a valve plate which is movable between an open position in which it lies next to the valve opening and releases the valve opening and a closed position in which the valve opening is covered, wherein the vacuum valve has a completely open state in which the valve plate is in its open position and a completely closed state in which the valve plate is in its closed position and is sealed relative to the valve body.
b) Description of the Related Art
There are different known embodiment forms of valves in which the valve plate is laterally adjacent to the valve opening in the open state and is displaceable into a position in which the valve opening is covered for closing the valve. Valves of this type are known as slide valves.
In a conventional embodiment form of valves of the type mentioned above, the valve plate is initially displaced from its open position into a position in which the valve opening is completely covered but the valve plate is raised from the valve seats arranged at the valve body. This displacement is carried out in the plane of the valve plate. The valve plate is subsequently set against the valve seat so that sealing is achieved relative to the valve body.
Slide valves of the type mentioned above are known, for example, from U.S. Pat. No. 4,052,036, U.S. Pat. No. 4,470,576, and U.S. Pat. No. 4,660,141. After the valve plate has achieved the state in which the valve opening is completely covered when closing the valve, the valve plate is spread apart for advancing the valve plate toward the valve body and for sealing relative to the latter. The contents of these patents are hereby adopted through reference.
Aside from valves in which the valve plate is displaceable in a straight line between its open position and its position in which the valve opening is covered, there are also known valves of this type in which the valve plate is swiveled around a swiveling axis extending perpendicular to the plane of the valve plate. Valves of this type are also known as pendulum slides or pendulum valves. In one embodiment form of a valve of this kind, the valve plate is spread apart in a manner analogous to valves that are displaceable in a straight line.
Further, there are known vacuum valves of the kind mentioned above in which L-shaped movements of the valve plate are carried out when closing the valve. In this connection, a displacement of the valve plate is initially carried out again in its plane (between the open position and the position in which the valve opening is completely covered) and, after reaching the position in which the valve opening is covered, a displacement is carried out vertical thereto. A valve of this type is known from U.S. Pat. No. 6,431,518B1, for example. Apart from valves with valve plates which are displaceable in a straight line proceeding from their open position, there are other valves in which the valve plate is swiveled around a swiveling axis extending perpendicular to its plane. In addition to L-movements, grinding movements (with movement components diagonal to the plane of the valve plate, particularly shortly before closure of the valve), also referred to as J-movements, are known.
Further, there are known slide valves in which the displacement of the valve plate and sealing of the valve are carried out only by a straight-line movement (in the principal plane of the valve plate), wherein the sealing surface and the sealing ring have a three-dimensional orientation or alignment. A design of this type is described, for example, in the British Patent Application GB 2 205 926 A whose contents are hereby likewise adopted through reference.
U.S. Pat. No. 5,577,707 discloses a slide valve in which an annular seal connection piece is provided for sealing the valve plate relative to the valve body in the completely closed state of the valve. The seal connection piece is mounted in the through-channel of the valve body forming the valve opening so as to be displaceable vertical to the plane of the valve plate and is accordingly sealed relative to the valve body. In the completely closed and sealed state of the valve, the seal connection piece is advanced toward the valve plate and is likewise sealed relative to it. The contents of this patent are hereby adopted through reference.
In slide valves which are constructed as regulating valves, the valve plate can be moved into various intermediate positions between its initial position and its end position by means of the correspondingly constructed drive of the valve plate, so that the cross section of the valve opening is adjustable in order to configure the conductivity of the valve in a controllable manner. Stepping motors, for example, can be used to drive the valve plate.
In some applications, however, the ability to fully regulate the cross section of the valve opening is not required and not even desirable. In this case, in addition to the completely open state and the sealed state of the valve, there is only a predetermined partially closed state in which the valve plate can be moved into an intermediate position determined by the drive between its open position and its closed position. Valves of this kind are also known as three-position valves and the drives used in this case, particularly pneumatic drives, are known as three-position drives. A disadvantage in these three-position valves consists in that the orifice opened in the intermediate position of the valve plate is not symmetric to the axis of the valve opening so that the gas flow through the valve is asymmetric, which is undesirable in various applications, for example, in semiconductor technology.